W202 - Strange transmission noise like whale song!

[thephatmaster]

Morning all,

I'm now getting a fascinating new sound from my W202 - an intermittent whine from somewhere in the transmission that sounds like whale song.

It started after I recently changed:
- my gearbox oil (see below, under heading 'the transmission oil change' for more details).
- my diff oil; and
- my propshaft centre bearing .

Steps taken to diagnose:

Being intermittent it is hard to diagnose - I will try to get a recording - but for now I have established the following:

- it occurs under load, even gentle load,

- I feel like it occurs most if the weather changes to colder overnight, however, it is not only present on colder days, and seems to "settle down" in longer cold periods.

- I drive the same journey every day. Some days it makes no noise whatsoever, some days it sings away the whole journey (within certain road speeds).

- is occurs between approximately 25 and 35 mph road speed;

- the noise goes through steps in pitch, seemingly randomly as if I am changing gear (which I am not - it is a manual transmission). It sounds to me like an old 1990's formula 1 simulation arcade game, or whale song.

- the noise happens irrespective of gear. It makes the same noise in 2nd, 3rd and 4th in the above road-speed band.

Steps taken to resolve:

- I haven't touched the centre bearing, which may be the cause - who knows?

- so far I have been mostly been faffing with oil levels in the trans / diff with the car at an angle (so as to not loose fluid from the filler hole):

- topped up the diff oil level: - this seemed to make it less likely to happen, and less likely to do more than a brief whine then settle down.

- topped up the transmission to 1.8l, which made it pretty reliably whine a tiny, tiny bit at the start of every journey (0.5 miles or so) - but then settle down to quiet.

- dropped the transmission oil level to 1.5l yesterday (thinking 1.8 was too much) - today it has been very very whiney for my whole journey to work - I will see what it does later on...


The transmission oil change:

My manual transmission has the part number 717417 07 652708, and I used the oil kindly recommended in this thread.

I initially filled the gearbox on roughly level ground and measured that I had pumped 1.6l of fluid into beforethe transmission before it overflowed out the filler.

I have since changed that to 1.8l (my understanding of the factory oil level) and then dropped it to 1.5l (the level given in the Haynes manual) to try and diagnose the whine noise.

 

[thephatmaster]

**can't find edit button** drove home, similar temperature etc - not a peep - strange

 

[thephatmaster]

I have a recordings of the sound now in AMR and WAV format - but the forum attachment dialogue simply says it won't accept the format - I've had a search but it is not clear to me what formats are acceptable - can anyone help?

 

[MercedesDriver]

Upload it on youtube as public and then share the link.

 

[thephatmaster]

Thanks for the idea @MercedesDriver.

Took some faff as it was an audio only file, but please see the video here

 

[MercedesDriver]

Because you have changed the propshaft bearing even the slightest play in the centre one could make the humming noise.
Pos.35 here PROPELLER SHAFT MERCEDES C-KLASSE [Car] [CHASSIS] (EUROPA)

 

[thephatmaster]

Thanks bt that link shows the earler propshaft. I have the facelift model with the press-on sealed centre bearing assembly which bolts to the body wit two bolts. It was that which which I changed (for a new one).

When you say play, what do you mean? The mounting holes to the body are elongated, but I tried to turn the propshaft by hand to make sure they were as centred as I could get them.

 

[thephatmaster]

I've now collected more data on the whining / singing noise by logging it and other variables (temperatures, speeds, length of car standing, fuel level etc) on a spreadsheet:

• It can be "cured" - e.g no noise at any road speed, for around 3-4 miles by spending over 20 seconds at 50+mph - this led me to think it is lubrication related (fluid level changes however do not affect the noise). The "cure" works overnight. I can drive at 50+mph, park-up and get 3-4 miles of silent running when I next drive, often days later.
• It no longer happens under load, it happens in gear (manual transmission) when coasting in-gear, and when coasting in neutral.
• It is not sensitive to atmospheric temperatures (occurs -3 to +20 degrees C), fuel level, passenger load, or engine coolant temperature.
• There is no effect on vehicle operation. The vehicle goes, stops, changes gear (manual) smoothly and gets the expected MPG.
• There are no fluid leaks.
• The noise is reasonably loud (loud enough for passengers to ask about it) and occurs in three bands:
  • It is present, changing pitch in two or three "steps" between 10-15mph
  • it is silent 15-20mph
  • Is present 20-27mph, the pitch getting higher with road speed
  • Is silent 27- 30mph
  • Is present 30-37mph, the pitch getting higher with road speed
  • 40+mph it is silent
  • There is a, seemingly separate and barely audible, rhythmic "warble" just below 30mph, and just below 40mph, which is sensitive to suspension movement. Though that may be because the movement causes tiny road-speed changes (I'm going to check the wheel bearings)

Further steps taken to diagnose:

• I have now added +100ml of fluid to both the differential and the (manual) transmission. No change in noise.
• I've checked for loose / rubbing parts. No issues.
• I've loosened the handbrake auto-adjust (which was slightly tight) - No change.
• I've had passengers listen for the location of the noise, to my ears it comes from right under the gear stick, or toward the passenger footwell. Others say towards the rear of the vehicle.

My next steps are:

• Check all four wheel bearings (as it's road speed related and the car is 20 years old);
• Consider replacing the (new) centre propshaft bearing with another.
• Perhaps try to get a better/updated recording of it.

Any ideas would be welcome

 

[Stratman]

As you've been rummaging in the transmission tunnel, take a look at the parking brake cable. They're known for rubbing against the propshaft and causing all sorts of weird, intermittent, hard to tie down noises.

 

[grober]

Does your car have a speedo cable driven off the gearbox. If so try disconnecting it at the gearbox end temporarily to test if the sound disappears?

 

[amazighman]

If you know someone with a hydraulic ramp , you can then put it in gear and listen

 

[Peterw202]

Did u ever find out what was making the noise as my w202 is making same noise it's automatic transmission.

 

[Peterw202]

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This is link to my utube video with sound my car is doing. It sounds like it's coming from under gear shifter.

 

[wongl]

Did you use the MB oil or MB spec oil?

 

[Peterw202]

Getting transmission oil/ filter changed this week. Not sure about what type of oil to be honest as the garage r getting it for me.

 

[wongl]

Getting transmission oil/ filter changed this week. Not sure about what type of oil to be honest as the garage r getting it for me.

Personally I wouldn't leave the choice of gearbox oil to the garage and would personally purchase these from MB directly myself to ensure the proper oil is used in what is a pretty infrequent service procedure. After all, MB gear oil are not that expensive, especially for something is only replaced every four to five years.

 

[thephatmaster]

As you've been rummaging in the transmission tunnel, take a look at the parking brake cable. They're known for rubbing against the propshaft and causing all sorts of weird, intermittent, hard to tie down noises.

I'll take a look next time I'm under there

Does your car have a speedo cable driven off the gearbox. If so try disconnecting it at the gearbox end temporarily to test if the sound disappears?

I believe the VSS signal comes from the ABS sensor, so no.

@wongl - for me, that information is in the OP (My manual transmission has the part number 717417 07 652708, and I used the oil kindly recommended in this thread.)

I've recorded some video of the noise - see from 23 seconds onwards - will try to do better once I've printed a longer gopro mount that means y'all can see the speedo. Like in @Peterw202 's car the noise comes from under the shifter, but I have a manual gearbox.

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[wongl]

- for me, that information is in the OP (My manual transmission has the part number 717417 07 652708, and I used the oil kindly recommended in this thread.)

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Sorry I still don't understand - the noise started after a transmission oil change, no? Logically it would suggest that the noise is somehow associated with the oil change, no? Unless there some other fault randomly developed coincidentally at the same time as the oil change?

Looking deeper into the oil change, it would appear that the transmission oil, which the general consensus in this forum, is critical for the smooth operation of the gearbox, was not sourced from MB. Instead it was sourced from Febi whose own data sheet does not state approved by MB.

Given that the noise is related to the oil change, and the oil used was not MB approved, are we ignoring the obvious cause here?

 

[thephatmaster]

the noise started after a transmission oil change, no? Logically it would suggest that the noise is somehow associated with the oil change, no?

That's 1/3 or so right, it started after:
- removal of R subframe, fuel tank and propshaft for a welding job
- trans oil change
- diff oil change
- propshaft centre brearing replacement

Lots of stuff was disturbed during that job.

Looking deeper into the oil change, it would appear that the transmission oil, which the general consensus in this forum, is critical for the smooth operation of the gearbox, was not sourced from MB. Instead it was sourced from Febi whose own data sheet does not state approved by MB.

Given that the noise is related to the oil change, and the oil used was not MB approved, are we ignoring the obvious cause here?

The oil was extensively researched in the other thread. It appears from the the identical part nos that Febi are the OEM for the 'MB' oil. For what it's worth my local stealer said I needed to use ATF, which appears not to be correct for later model gearboxes (including the one with my part no).

 

[wongl]

That's 1/3 or so right, it started after:
- removal of R subframe, fuel tank and propshaft for a welding job
- trans oil change
- diff oil change
- propshaft centre brearing replacement

Lots of stuff was disturbed during that job.

Thanks for sharing more information since your original post.

I hope you will get to the bottom of the whale song noise and report back with your findings.